A nozzle for a blowing machine comprises an end which is shaped to communicate sealingly with the inside of a blank.
Blowing machines are known in which the end of the nozzle, in the functional position, cooperates positively with the neck of the blank either by sealingly abutting against the lip (edge) of the neck of the blank, or being sealingly fitted into or onto the neck of the blank.
The end of the nozzle (sometimes known as the nozzle tip) is, for example, truncated, the diameter at the base of the nozzle being less than that of the opening of the blank. The seal during the blowing is thus ensured by the contact between the truncated cone and the internal peripheral edge of the lip of the blank.
Blowing machines are also known in which the end of the nozzle is bell-shaped and larger than the neck of the blank and covers said neck of the blank by bearing at the front, sealingly, against the face of the mold on which the neck of the blank projects (see for example the document FR 2 764 544).
In the known manner, the nozzle is designed to be entirely or partially mobile, axially above the blow mold between:                an upper position or raised position in which the nozzle is not functional (the opening and closing of the mold allowing the loading of a blank and the discharge of the molded container)        and a lower position or blowing position in which the end of the nozzle cooperates sealingly either with the neck of the blank or with the face of the mold above which the neck of the blank projects and in which the nozzle is functional.        
The blowing of bottles made of PET from preforms is usually carried out in stages:                a step of pre-blowing the blank using a moderately pressurized fluid (generally air) (for example 7×105 Pa to 12×105 Pa), generally accompanied by mechanical axial stretching by means of said drawing rod        then a blowing step itself, at high pressure, for example 40 bars (40×105 Pa)        and finally an exhaust (or degassing) step with the discharge of the pre-blowing/blowing air. If necessary, the degassing air is recovered. A silencer mechanism is assigned to the degassing.        
The pre-blowing typically leads to an increase in pressure of 0 to 13 bars in approximately 100 milliseconds. The blowing leads typically to an increase in pressure up to a nominal value of 23 bars in approximately 100 milliseconds. The degassing is typically carried out in approximately 300 milliseconds. The pre-blowing and the blowing may be partially simultaneous. In the past, controlling the pressures has been extremely important for the quality of the blown products.
The stretching of a blank made of PET and the pre-blowing at moderate pressure (for example 7×105 Pa) lead to an axial elongation velocity in the order of 0.8 to 1.2 m/s, controlling this velocity being important for the quality of the blown product. The radial stretching obtained by blowing at high pressure (for example 40×105 Pa) allows the material to be forced against the walls of the mold which is cooled down, for example, by the internal circulation of cooled water.
It is frequently possible to achieve 50,000 bottles per hour in industrial blowing machines. These high-speed machines are of the rotating type and comprise several tens of molding devices mounted on the periphery of a carousel.
To carry out the pre-blowing/blowing/discharge steps, conventionally three solenoid valves are sequentially controlled which, on the one hand, are connected respectively to a source of moderately pressurized fluid, a source of highly pressurized fluid and an exhaust and which, on the other hand, are connected to the nozzle.
Amongst the technical problems to be solved, it is noteworthy that a blowing machine of the type under consideration consumes very large amounts of pressurized fluid, of which one portion is not necessary for the manufacture of the article, whether it is at moderate or high pressure.
The blowing of a hollow body of one liter by stretch blowing typically requires 40 liters of fluid if the blowing pressure is 40×105 Pa.
It has to be understood that the only required volume for the blowing operation is the volume of the container brought into its final shape against the walls of the mold cavity of the mold, in other words substantially the volume of the mold cavity.
In contrast, all the volumes between the outlet of the pre-blowing or blowing solenoid valve and the neck of the container are volumes which are not actually required for the deformation of the blank and are thus dead volumes.
For manufacturing bottles by blowing, the dead volume thus represents the difference between the total volume to be put under pressure and the internal volume of the bottle at the edge of the lip or required volume.
At each step for pre-blowing and blowing a blank, these dead volumes are filled with pressurized fluid in the same manner as the required volume, which involves a production of pressurized fluid which is substantially greater than the actual requirement. In the majority of blowing machines of the prior art, the dead volumes are of a size which is not inconsiderable relative to the required volumes.
Any reduction in these dead volumes proves beneficial in terms of possible reduction of the power of the fluid compressor and thus its cost, and in terms of reducing the electrical energy required by the functioning of the compressor. The continuous production of pressurized fluid (air) in a large quantity leads to a very high consumption of electrical energy for the functioning of the compressor(s).
As a result, there is a constant and urgent need on the part of the users of said blowing machines for a reduction which is as large as possible of the quantity of pressurized fluid used, so as to reduce the consumption of electrical energy.
It is also noteworthy that the blowing machines function at ever increasing speeds. The production rates are in the order of 1200 to 2000 containers per hour and per mold in the stretch blowing machines of the applicant. Even when anticipating very long service lives for the solenoid valves (in the order of 30 million cycles), maintenance and adjustment operations on said solenoid valves remain relatively frequent.
In a first design of the applicant, the solenoid valves form a unit mounted directly on the body of the nozzle, at the position of the tube connector referenced 23 in FIG. 1 of the document FR 2 764 544.
However, in this first design which is currently in existence, the juxtaposition of the two respective bodies of the solenoid valve unit and of the nozzle also involves fluid passages of considerable length which results in a dead volume which is still very large in terms of consumption.
A second design, also from the applicant, has been the subject of a French patent application filed on 23 Jun. 2004 under the number FR 04/06844 (publication number FR 2 872 082).
According to this second design, the nozzle slides in a body provided with three housings, in each of which a solenoid valve is incorporated: the pre-blowing solenoid valve, the blowing solenoid valve and the exhaust solenoid valve. This nozzle surrounds a drawing rod which is coaxial thereto.
An annular space for the passage of air is defined in said body by the drawing rod and the internal face of the nozzle. Each housing containing a solenoid valve is connected to said annular space by a radial pipe.
A fourth housing in the body may receive a recycling solenoid valve, which is actuated after the blowing, whilst the exhaust solenoid valve is actuated last of all for the rapid removal of the residual blowing fluid.
The housings for solenoid valves are equidistant, substantially cylindrical, and parallel or perpendicular to the sliding axis of the nozzle. Said housings are, for example, radial relative to said nozzle axis.
When each solenoid valve is arranged radially relative to the central bore of the body in which the nozzle slides, the mobile core of each solenoid valve may be mounted directly in the housing which has been machined to this end, and the front face of said mobile core may be flush with the lateral wall of the bore and be within the continuation of this lateral wall. As a result of this design, the dead volume downstream of the mobile core is reduced very significantly.
This second design has several drawbacks. In particular, it requires free access to be allowed to the different sides of the body, which may not be possible in certain configurations of machine.
More specifically, according to a particular embodiment, the blowing nozzles are placed in a blowing machine adjacent to one another, on a carousel, adjacent to the periphery of said carousel.
In order to increase production rates, it would be necessary to increase the number of nozzles around this central shaft or to increase the overall volume of the machine, this latter solution not being desirable.
Access to the lateral parts of a nozzle may therefore be quite difficult and awkward in the case where the number of nozzles on the carousel exceeds a certain amount, resulting in a limited space for intervention between two successive nozzles.
It is appropriate, therefore, to limit the presence of parts fixed to the lateral faces of a nozzle to avoid maintenance operations on these faces and thus to be able to increase the number of nozzles around the same central shaft of a carousel whilst not increasing the overall volume of the machine.
A third design is illustrated by the document EP 1 328 396.
In this third design, the valve support is of rectangular section and a high pressure valve, a low pressure valve, and two exhaust valves are arranged at the same height on two opposing faces of this valve support. Internal pipes which are as short as possible place the valve chambers in fluidic connection with the sliding axial orifice of the drawing rod.
This third design proves to be impractical in usage. As mentioned above, high-speed machines are rotary. When the valve support units of the type disclosed in the document EP 1 328 396 are used, the valves are, for an observer positioned in front of a blow mold, positioned to the right and to the left of each support unit, the lateral space requirement of these valves and of their control members being very disadvantageous for the compactness of the machine and as has been explained above relative to the second design.
According to a fourth design as disclosed in the document EP 1 535 720, a fluid flow control assembly for a blowing machine is shown, this assembly comprising supply and discharge pipes for fluid, a blow pin and a plurality of valves to control the blowing air in the different pipes.
However, according to this prior art, the different valves are arranged tightly relative to the blow pin and it is thus necessary to dismantle the body which houses the blow pin if the valves have to be repaired or changed.
It would, therefore, be particularly advantageous to produce an assembly for controlling the blowing which does not require the blow pin to be dismantled or to be acted upon when maintenance or repair operations have to be carried out on the valves for controlling blowing fluids.
The object of the invention is, therefore, to attempt to satisfy, as far as possible, these constant demands of users and to propose an improved design of blowing machine which leads to a better compromise between:                on the one hand low dead volumes in the circuit for supplying pressurized fluid;        and, on the other hand, structural assemblies for controlling the flow of a blowing fluid for a blowing machine which are light-weight, compact, of easy maintenance and with rapid access to the valves without restrictions to the spatial requirement, in particular laterally, due to the presence of a plurality of functional assemblies located around a central shaft of the carousel. The assembly according to the invention also makes it possible to avoid dismantling the unit housing the blow pin during operations for maintenance or replacing the valves.        